An oscillator includes first, second and third inverters (1, 2, 3) connected in series. A feedback path is connected from the output terminal of the third inverter (3) to the input terminal of the first inverter 1 through a resistor (5) while a second feedback path is connected from the output terminal...http://www.google.fr/patents/US7129798?utm_source=gb-gplus-shareBrevet US7129798 - Oscillator circuit having stable frequency
